Characteristics of Patients with Coronavirus Disease 2019 (COVID-19) and Seasonal Influenza at Time of Hospital Admission: a Single Center Comparative Study

Abstract BackgroundFor the winter season 2020/2021, co-circulation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza viruses A/B is expected. From a clinical point of view, differentiation of these two acute respiratory illnesses is crucial for optimal patient management. We therefore aimed to detect clinical differences between Coronavirus Disease 2019 (COVID-19) and seasonal influenza patients at time of hospital admission.MethodsIn this single-center observational study, we included all consecutive patients hospitalized for COVID-19 or influenza between November 2019 and May 2020. Data were extracted from a nationwide surveillance program and from electronic health records. COVID-19 and influenza patients were compared in terms of baseline characteristics, clinical presentation and outcome. We used recursive partitioning to generate a classification tree to discriminate COVID-19 from influenza patients.ResultsWe included 96 COVID-19 and 96 influenza patients. Median age was 68 vs. 70 years (p=0.90), 72% vs. 56% (p=0.024) were males, and median Charlson Comorbidity Index (CCI) was 1 vs. 2 (p=0.027) in COVID-19 and influenza patients, respectively. Time from symptom onset to hospital admission was longer for COVID-19 (median 7 days, IQR 3-10) than for influenza patients (median 3 days, IQR 2-5, p<0.001). Other variables favoring a diagnosis of COVID-19 in the classification tree were higher systolic blood pressure, lack of productive sputum, and lack of headache. The tree classified 86/192 patients (45%) into two subsets with ≥80% of patients having influenza or COVID-19, respectively. In-hospital mortality was higher for COVID-19 patients (16% vs. 5%, p=0.018).ConclusionDiscriminating COVID-19 from influenza patients based on clinical presentation is challenging. Time from symptom onset to hospital admission is considerably longer in COVID-19 than in influenza patients and showed the strongest discriminatory power in our classification tree. Although they had fewer comorbidities, in-hospital mortality was higher for COVID-19 patients.